PROJECT SUMMARY/ABSTRACT The purpose of this Mentored Research Scientist Development Award (K01) is to provide the candidate with training and expertise needed to become an independent scientist who conducts implementation research at the intersection of mental and substance use disorders (MSD) and HIV. The candidate plans to generate knowledge and advance understanding of the impact of MSD on key HIV treatment outcomes in the context of universal test and treat (UTT) strategies in low-resource settings and identify promising implementation strategies to integrate and scale evidence-based MSD interventions within HIV care programs. To achieve these goals, the candidate plans to supplement her training in epidemiology and social work with training in: 1) implementation science, focused on integrating evidence-based MSD interventions into HIV clinics in low- resource settings 2) mixed methods, and 3) evidence-based MSD interventions. Training goals will be met through graduate-level coursework, scientific conferences, directed readings, intensive mentorship, and experiential learning through the proposed research. WHO guidelines call for antiretroviral therapy for all people living with HIV regardless of CD4 cell count. Because MSD are both common among people living with HIV and drive suboptimal HIV care outcomes, UTT goals are unlikely to be achieved without attention to MSD in HIV care programs. The extent to which MSD may be major barriers to the successful implementation of UTT in low-resource settings is not known. In many low-resource settings, HIV providers neither screen nor treat patients for MSD, leaving a need for integration of evidence-based MSD care. The candidate proposes to study MSD among PLWH in the context of UTT implementation in Cameroon, which began UTT implementation in 2016. Cameroon is a WHO 2020 Fast Track country and has the highest HIV prevalence in West and Central Africa, low ART coverage, and high prevalence of alcohol use disorders and depressive symptoms. Using mixed methods, the candidate will examine the impact of MSD on HIV treatment outcomes in the context of UTT and identify the most important barriers and facilitators to integration of evidence-based MSD interventions into HIV care at three HIV clinics in Cameroon. She will use information gained at these three clinics to systematically assess implementation gaps and capacity to integrate evidence-based MSD interventions at 57 HIV care sites in sub-Saharan Africa where UTT is taking place to inform integration on a larger scale. The proposed research will be embedded in the International Epidemiology Database to Evaluate AIDS (IeDEA) network, the largest global HIV/AIDS implementation research network of HIV care cohorts. Identification of key modifiable patient-, provider-, and health facility-level factors that influence implementation and sustained uptake of evidence-based MSD interventions in HIV care, particularly in the context of UTT, is essential to identify and eventually test optimal implementation strategies to program, scale and sustain integrated care for MSD and HIV in low-resource settings.